Archive for January 2007

ABSTRACT: In this communication we report the lowered thermal stability of sulfur/chlorate mixtures in contact with glass surfaces. Ignition temperatures as low as 100 °C were found in glass test tubes and are about 15 °C less than for the same mixture in a cardboard fireworks tube.

Introduction: During the mid 1980’s, I was the President and General Manager of San Diego Fireworks, Inc. At many of our Pyrotechnic Safety and Training Seminars, I was asked about the correlation between mortar length and altitude attained by aerial shells. Further, I have overheard many theories relating to a “vacuum” created within a mortar, if that mortar is longer than some optimum length. Others have made statements indicating that exceptionally long mortars would project shells well beyond “normal” altitudes for given sizes of shells. Upon reaching saturation of these various theories, our staff decided to perform some basic tests to see if any of these theories had merit. Prior to making the determination to conduct this field test, we had the opportunity to view videotape produced by a Japanese firm. This videotape showed shells being fired from a thickwalled glass mortar. Our observations indicated that there was a considerable amount of gas generated by the lift charge and that the vast majority of this gas was produced well after the shell had left the open end of the mortar during launch. Although our methods were not purely scientific, in that we did not use precise measurement recognized in the industry as acceptable and would be able to determine if the theories were in fact accurate or erroneous. We were not looking for precise data, but data sufficient to determine if these theories warranted further investigation.

ABSTRACT: Two tracer compositions were formulated based on magnesium, strontium nitrate and sodium nitrate with unsaturated non-halo and halo polyesters as binders. They were characterized for mechanical properties, thermal behaviour, burning rate, luminous output, and impact, friction and spark sensitivities. The data show that the composition with chloropolyester as binder is better for tracer compositions.

ABSTRACT: The expert witness who over-infers his data through the misuse of adjectives of comparison opens himself up to cross-examination that can and will discredit his work product. This paper uses the example of forensic analysis of black powder explosive to demonstrate that one can not categorically “match” one Black Powder sample to another or very often one complex chemical system to another and that even if this were possible, such “matches” may have limited probative value. The paper also explores the legal obligation of the expert to reveal to the prosecutor, court and trier-of-fact the limitations of the probative value of the evidence where those limitations might be considered to be exculpatory information.

ABSTRACT: The morphology (size, shape and surface features) of the constituent particles in a pyrotechnic composition affects its performance. This is particularly true of metal fuel particles in the composition. Particle morphology can also constitute an important part of forensically establishing a match between materials of known origin and evidence. This article catalogs and briefly discusses some characteristic features commonly associated with metal fuels in pyrotechnic compositions.

ABSTRACT: Propellants used for pyrotechnics are composed of energetic materials that produce hightemperature and high-pressure gaseous products. The propellants are classified into three types by their physical structure and the ingredients used: (1) homogeneous propellants consisting of chemically bonded oxidizer and fuel components in the same molecule, (2) heterogeneous propellants consisting of physically mixed oxidizer and fuel components, and (3) granulated propellants consisting of energetic solid particles. While the energy content of a propellant is determined by the chemical properties of the ingredients, the physical properties and chemical processes of the ingredients determine the ballistic characteristics such as burn rate and pressure and temperature sensitivities.

ABSTRACT: The effects of stoichiometry and particle size on the thermal stability and sensitiveness of sulfur/chlorate mixtures have been investigated. Mixtures containing small particles and approximately 5% sulfur were shown to be the least thermally stable. Sulfur/chlorate mixtures containing a third component have also been investigated and compositions with up to 70% added material gave similar low ignition temperatures to mixtures of the two components. All compositions containing sulfur/chlorate were found to be friction sensitive and had limiting loads below the 80 N UN transport criterion. When iron was the third component, the compositions were also impact sensitive, with Limiting Impact Energies below the 2 J UN transport criterion.

ABSTRACT: A chemical analysis of a selection of fireworks has been made. The products were chosen to represent the typical use of consumer fireworks in Sweden 1998. The purpose of the assignment was to estimate to what extent consumer fireworks contribute to the total emission of some undesirable elements in Sweden. Six consumer items were examined (two of them being multi item kits). Nineteen elements were analyzed, but focus was made on the environmentally undesirable elements arsenic, cadmium, lead and mercury. The conclusion was that, as far as arsenic, cadmium and mercury are concerned, the contribution from consumer fireworks is insignificant compared with the total emission and deposition within the country. The emission of lead, which is a well-known constituent in crackling fireworks effects, can at most be 0.8 % of the total emission and deposition in the country. The figures in this paper do not provide any evidence in favor of restricting the lead content of fireworks.

ABSTRACT: An interest in plume spectroscopy led to the development of a labscale Hybrid Rocket Facility at the University of Arkansas at Little Rock (UALR). The goal of this project was to develop a reliable, consistent rocket motor testbed for the development of plume spectroscopy instrumentation. Hybrid motor technology was selected because it has proven to be safe and inexpensive to operate. The project included the design and construction of the labscale hybrid rocket motor, the supporting facility, the instrumentation and computer control of the motor, and the characterization of this particular thruster, including the regression rate of hydroxyl- terminated polybutadiene (HTPB) fuel grains. For plume spectroscopy experiments, the fuel is doped with metal salts, to simulate either solid motors or liquid engines. It was determined the labscale hybrid motor produces a reliable and consistent plume, resulting in an excellent tool for the development of plume spectroscopy and other instrumentation.

At first glance, this 117-page paperback book[1] looks very promising. According to the publisher’s description, the book “is aimed at students with ‘A’ level qualifications or equivalent. The style is concise and easy to understand, and the theory of fireworks is discussed in terms of well-known scientific concepts wherever possible. It will also be a useful source of reference for anyone studying pyrotechnics as applied to fireworks.”[1a] The author of the work, Michael S. Russell, is a research chemist with a background in military and marine pyrotechnics, and he has worked as a firework display operator. He should be well qualified to write on this subject.